Add additional model and integration tests

This commit adds new tests for a better coverage.

integration/
  * home
  * supplier

models/
  * article
  * delivery
  * group_order_article
  * supplier

also adds a new factory for delivery

Co-authored-by: viehlieb <pf@pragma-shift.net>
Co-authored-by: Tobias Kneuker <tk@pragma-shift.net>

spec/models/article_spec.rb

@@ -15,6 +15,38 @@ describe Article do
     expect(article).to be_deleted
   end
 
+  describe 'convert units' do
+    it 'returns nil when equal' do
+      expect(article.convert_units(article)).to be_nil
+    end
+
+    it 'returns false when invalid unit' do
+      article1 = build :article, supplier: supplier, unit: 'invalid'
+      expect(article.convert_units(article1)).to be false
+    end
+
+    it 'converts from ST to KI (german foodcoops legacy)' do
+      article1 = build :article, supplier: supplier, unit: 'ST'
+      article2 = build :article, supplier: supplier, name: 'banana 10-12 St', price: 12.34, unit: 'KI'
+      new_price, new_unit_quantity = article1.convert_units(article2)
+      expect(new_unit_quantity).to eq 10
+      expect(new_price).to eq 1.23
+    end
+
+    it 'converts from g to kg' do
+      article1 = build :article, supplier: supplier, unit: 'kg'
+      article2 = build :article, supplier: supplier, unit: 'g', price: 0.12, unit_quantity: 1500
+      new_price, new_unit_quantity = article1.convert_units(article2)
+      expect(new_unit_quantity).to eq 1.5
+      expect(new_price).to eq 120
+    end
+  end
+
+  it 'computes changed article attributes' do
+    article2 = build :article, supplier: supplier, name: 'banana'
+    expect(article.unequal_attributes(article2)[:name]).to eq 'banana'
+  end
+
   it 'computes the gross price correctly' do
     article.deposit = 0
     article.tax = 12